In 3GPP Long-Term Evolution (LTE) networks, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of base stations, e.g., evolved Node-Bs (eNBs) communicating with a plurality of mobile stations referred as user equipment (UEs). Orthogonal Frequency Division Multiple Access (OFDMA) has been selected for LTE downlink (DL) radio access scheme due to its robustness to multipath fading, higher spectral efficiency, and bandwidth scalability. Multiple access in the downlink is achieved by assigning different sub-bands (i.e., groups of subcarriers, denoted as resource blocks (RBs)) of the system bandwidth to individual users based on their existing channel condition. In LTE networks, Physical Downlink Control Channel (PDCCH) is used for dynamic downlink (DL) or uplink (UL) scheduling of Physical Downlink Shared Channel (PDSCH) or Physical Uplink Shared Channel (PUSCH) transmission. The DL/UL scheduling information carried by PDCCH is referred to as downlink control information (DCI).
Various methods of control-less transmission have been adopted in mobile communication networks to improve efficiency and system capacity. For Wideband Code Division Multiple Access (WCDMA) used in Universal Mobile Telecommunications System (UMTS), blind transport format detection (BTFD) is adopted. UE will blindly detect the possible transport format without explicit signaling. The possible payload sizes are 12.2 kbps, 7.95 kbps, and 1.95 kbps. For High Speed Downlink Packet Access (HSDPA), a control channel (HS-SCCH) is not transmitted for the initial transmission of a data channel (HS-PDSCH). UE will blindly decode the data on HS-PDSCH with predefined control information, under maximum of four transport block size ranging from 137˜1483. If the UE is unable to blindly decode the initial transmission successfully, then the data shall be retransmitted accompanied by HS-SCCH type-2. For LTE, semi persistent scheduling (SPS) has been proposed. The eNB can configure UE in SPS and use PDCCH to activate SPS. The UE will periodically decode the PDSCH in the SPS subframe configured by higher layer, e.g., via radio resource control (RRC) signaling, by the activation PDCCH. The UE does not do blind detection but follows a predefined transport block size indicated by DCI.
Narrowband IoT (NB-IoT) is a Low Power Wide Area Network (LPWAN) radio technology standard that has been developed to enable a wide range of devices and services to be connected using cellular telecommunications bands. NB-IoT is a narrowband radio technology designed for the Internet of Things (IoT), and is one of a range of Mobile IoT (MIoT) technologies standardized by the 3GPP. For cellular narrowband Internet of Things and New Radio (NB-IoT/NR), it can be envisioned for some applications, there is only a small amount of data for infrequent traffic such as acknowledgement and network command/RRC signaling. The defined payload size is 12 bytes/message for uplink and 8 bytes/message for downlink. The uplink and downlink peak rate ranges from 20˜250 kbps. Large control overhead incurs for this kind of small packet transmission. Therefore, it is desirable to introduce control-less transmission to avoid unnecessary overhead and increase system capacity for cellular NB-IoT/NR.